Birn Rasmus M, Diamond Jason B, Smith Monica A, Bandettini Peter A
Laboratory of Brain and Cognition, National Institute of Mental Health, NIH, 10 Center Dr., Bldg. 10, Rm. 1D80 Bethesda, MD 20892-1148, USA.
Neuroimage. 2006 Jul 15;31(4):1536-48. doi: 10.1016/j.neuroimage.2006.02.048. Epub 2006 Apr 24.
Subtle changes in a subject's breathing rate or depth, which occur naturally during rest at low frequencies (<0.1 Hz), have been shown to be significantly correlated with fMRI signal changes throughout gray matter and near large vessels. The goal of this study was to investigate the impact of these low-frequency respiration variations on both task activation fMRI studies and resting-state functional connectivity analysis. Unlike MR signal changes correlated with the breathing motion ( approximately 0.3 Hz), BOLD signal changes correlated with across-breath variations in respiratory volume ( approximately 0.03 Hz) appear localized to blood vessels and regions with high blood volume, such as gray matter, similar to changes seen in response to a breath-hold challenge. In addition, the respiration-variation-induced signal changes were found to coincide with many of the areas identified as part of the 'default mode' network, a set of brain regions hypothesized to be more active at rest. Regions could therefore be classified as being part of a resting network based on their similar respiration-induced changes rather than their synchronized neuronal activity. Monitoring and removing these respiration variations led to a significant improvement in the identification of task-related activation and deactivation and only slight differences in regions correlated with the posterior cingulate at rest. Regressing out global signal changes or cueing the subject to breathe at a constant rate and depth resulted in an improved spatial overlap between deactivations and resting-state correlations among areas that showed deactivation.
受试者的呼吸频率或深度的细微变化，在低频（<0.1Hz）休息时自然发生，已被证明与整个灰质和大血管附近的功能磁共振成像（fMRI）信号变化显著相关。本研究的目的是调查这些低频呼吸变化对任务激活功能磁共振成像研究和静息态功能连接分析的影响。与与呼吸运动相关的磁共振信号变化（约0.3Hz）不同，与呼吸量的跨呼吸变化相关的血氧水平依赖（BOLD）信号变化（约0.03Hz）似乎局限于血管和高血容量区域，如灰质，类似于屏气挑战时所见的变化。此外，发现呼吸变化引起的信号变化与许多被确定为“默认模式”网络一部分的区域一致，这是一组假设在休息时更活跃的脑区。因此，区域可以根据其相似的呼吸诱导变化而不是同步的神经元活动被分类为静息网络的一部分。监测和消除这些呼吸变化导致与任务相关的激活和失活的识别有显著改善，并且与静息时后扣带回相关的区域只有轻微差异。去除全局信号变化或提示受试者以恒定的速率和深度呼吸，导致失活区域之间的失活和静息态相关性的空间重叠得到改善。
